Volume 48, Issue 2, Pages 329-343 (October 2005) Protein Synthesis-Independent Plasticity Mediates Rapid and Precise Recovery of Deprived Eye Responses  Thomas E. Krahe, Alexandre E. Medina, Ruben E. de Bittencourt-Navarrete, Raymond J. Colello, Ary S. Ramoa  Neuron  Volume 48, Issue 2, Pages 329-343 (October 2005) DOI: 10.1016/j.neuron.2005.09.016 Copyright © 2005 Elsevier Inc. Terms and Conditions

Figure 1 Rapid Recovery of Ocular Dominance Domains Revealed by Optical Imaging Maps of ocular dominance obtained from different animals are shown in the left column, where dark areas represent regions that responded best to gratings presented to the right eye and white areas represent regions that responded best to the same gratings presented to the left eye. White areas completely dominate V1 and V2 of the left hemisphere in a monocularly deprived animal (MD, [A]), whereas dark regions reflect recovery following restoration of binocular vision (B–D). Monocular response maps for the left and right eyes are shown in the center and right columns, respectively. Dark areas in monocular response maps represent visual response. In the left hemisphere, lack of response to stimulation of the deprived (right) eye in a monocularly deprived animal (A) contrasts with the robust response to stimulation of the recovering (right) eye in additional animals following restoration of binocular vision (B–D). Note the similarity between the 4 hr recovery ferret (D) and the normal ferret (E). In the right hemisphere, only weak responses to stimulation of the deprived (right) eye were observed after 4 hr of binocular recovery (F); much stronger responses to stimulation of the recovering eye (right) were detected following 4 days of binocular vision (G). The craniotomies exposed areas V1 and V2 (White et al., 1999), with rostral, shown at top and medial, at right (left hemisphere) or left (right hemisphere). Scale bar, 3 mm. Neuron 2005 48, 329-343DOI: (10.1016/j.neuron.2005.09.016) Copyright © 2005 Elsevier Inc. Terms and Conditions

Figure 2 Quantitative Assessment of Ocular Dominance Maps Ocular dominance histograms for recordings in the left hemisphere are shown in which the x axis represents classes of gray values (0 to 255, 0 = black and 255 = white) and the y axis indicates the number of pixels (in percentages) found for each gray value class. Darker (0–101) and lighter (153–255) pixels indicate responses dominated by the right (contralateral) and left (ipsilateral) eyes, respectively. (A and B) Animals deprived for 6 days ([B], n = 4) showed a pronounced ocular dominance shift toward the experienced (left) eye relative to normal animals ([A], n = 7). (C and D) Recovery of responses to the previously deprived (right) eye was already evident at 0.5–2 hr of binocular vision ([C], n = 4), and at 4 hr ([D], n = 7), animals showed a normal ocular dominance profile (compare [D] to [A]). Error bars indicate ±SEM. (E) Contralateral bias index scores (CBIOI, see the Experimental Procedures) are plotted for normal, monocularly deprived, and binocularly recovered animals. Each open circle represents the CBIOI for an individual animal, and the horizontal bars represent the mean CBIOI of each group. The CBIOI scores for the right hemisphere of 4 hr (n = 4) and 3 to 4 days (n = 4) binocularly recovered animals are also plotted (open triangles). For purposes of comparison, the CBIOI scores for the right hemisphere were subtracted from 1. After 6 days, but not 4 hr, of MD, a striking reduction in CBIOI values reflected increased predominance of the open ipsilateral eye. Following restoration of binocular vision, progressive recovery was seen in the left hemisphere so that after 4 hr of recovery, the CBIOI distribution is similar to normal. In the right hemisphere, however, CBIOI scores at 4 hr of binocular vision did not differ from the scores at 6 days of MD. BR, binocular recovery; cont, contralateral; ipsi, ipsilateral; RE, right eye; LE, left eye. Neuron 2005 48, 329-343DOI: (10.1016/j.neuron.2005.09.016) Copyright © 2005 Elsevier Inc. Terms and Conditions

Figure 3 Rapid Recovery of Deprived Eye Response and Cortical Binocularity Revealed by Single-Unit Recordings (A–F) Ocular dominance distributions for neurons located in the left V1 show that 4 hr of MD ([B], 120 cells, n = 4) did not induce a shift toward the ipsilateral (left) eye, whereas 6 days of MD induced an almost complete loss of deprived eye responses ([C], 218 cells, n = 8). Following 1–3 hr of binocular vision, animals showed a pronounced recovery of cortical binocularity ([D], 223 cells, n = 5). At 4 hr of recovery ([E], 331 cells, n = 8), ocular dominance profiles were similar to normal ([A], 178 cells, n = 6). A similar profile was also seen with 1–5 days of binocular vision after 6 days of MD ([F], 269 cells, n = 6). Error bars indicate ±SEM. (G) Contralateral bias index scores (CBI) are plotted for the left hemisphere of normal, monocularly deprived, and binocularly recovered animals. The CBIs for the right hemisphere of binocularly recovered animals (4 hr, 124 cells, n = 4; 12 hr, 243 cells, n = 5; 3–4 days, 90 cells, n = 4) are also plotted (open triangles). For purposes of comparison, the CBI scores for the right hemisphere were subtracted from 1. Each symbol represents the CBI for an individual animal, and horizontal bars represent the mean CBI of each group. CBI values in the left hemisphere were markedly reduced relative to normal following 6 days of MD, but rapidly recovered to normal values following restoration of binocular vision. In the right hemisphere, however, normal CBI values for most animals were only restored after 3–4 days of binocular vision. BR, binocular recovery; cont, contralateral; ipsi, ipsilateral; RE, right eye; LE, left eye. Neuron 2005 48, 329-343DOI: (10.1016/j.neuron.2005.09.016) Copyright © 2005 Elsevier Inc. Terms and Conditions

Figure 4 Rapid Recovery of Deprived Eye Responses in Different Cortical Layers (A–C) Nissl-stained V1 coronal sections from three recovered animals illustrating microelectrode tracks. Arrowheads indicate electrolytic lesions. (D–F) Ocular dominance distributions were determined for cells located in layers II/III ([D], 63 cells), layer IV ([E], 80 cells), and V/VI ([F], 95 cells) from six animals that had their right eyelids closed for 6 days and then were allowed 4 hr of binocular vision. Electrode penetrations (n = 15) were made in the left V1. Scale bar, 300 μm. Neuron 2005 48, 329-343DOI: (10.1016/j.neuron.2005.09.016) Copyright © 2005 Elsevier Inc. Terms and Conditions

Figure 5 Restoration of Deprived Eye Orientation Domains following 4 Hr of Binocular Recovery (A–C) Examples of maps of orientation preference for left and right eyes from different animals. The polar maps for each eye are also shown (below differential maps), where brightness and colors represent selectivity and preference, respectively. Normal orientation map (A) was lost for the deprived (right) eye in a 6 day MD animal (B), but recovered in another animal deprived for 6 days and then allowed 4 hr of binocular vision (C). The craniotomies exposed areas V1 and V2 in the left hemisphere (White et al., 1999), with medial represented to the right and rostral to the top of the figure. Scale bar, 3 mm. (D–F) Quantitative assessment of orientation selectivity in normal (n = 6), deprived (MD, n = 4) and recovered (BR, n = 7) animals. Orientation selectivity indices (OSIOI) were computed from cardinal and oblique difference images and from magnitude maps (see the Experimental Procedures). As expected, 6 days of MD significantly decreased the deprived (right) eye OSIOI values compared to the experienced (left) eye values ([D], [E], and [F], respectively: ∗∗∗p < 0.001, ∗∗p < 0.01, ∗p < 0.05, Student's t test). Four hours after restoration of binocular vision, orientation selectivity of the previously deprived (right) eye was restored in all cases. Error bars indicate ±SEM. Neuron 2005 48, 329-343DOI: (10.1016/j.neuron.2005.09.016) Copyright © 2005 Elsevier Inc. Terms and Conditions

Figure 6 Rapid Restoration of Neuronal Orientation Selectivity for the Recovering Eye (A and B) Orientation selectivity index (OSI) histograms created from responses to stimulation of the recovered (right) and experienced (left) eyes of eight animals after 6 days of MD followed by 4 hr of binocular recovery (left eye, 40 cells; right eye, 66 cells). The solid line (closed symbols) shows the OSI distributions for the dominant (left or right) eye of normal (nondeprived) animals (118 cells, n = 6). (C and D) Plots of OSIs for 20 cells in which responses to stimulation were recorded for each eye. These cells were recorded from five animals that were monocularly deprived for 6 days and then allowed 4 hr of binocular vision. Values sorted in ascending order for the experienced (left) eye revealed similar distributions for the two eyes. (E and F) Polar plots of single-unit responses computed from the same 20 cells shown in (C) and (D). (E) Each color line plots the normalized responses of a single neuron at different orientations relative to optimal. Note the similarity of the polar plots observed for the recovered eye (green lines) and the experienced eye (red lines). (F) Median of the recovered (green) and experienced (red) eye responses shown in (E) reveals similar orientation tuning for the two eyes. All recordings were made in the left hemisphere. Opt, optimal; Orth, orthogonal. Neuron 2005 48, 329-343DOI: (10.1016/j.neuron.2005.09.016) Copyright © 2005 Elsevier Inc. Terms and Conditions

Figure 7 Intracortical Infusion of CHX Suppresses Protein Synthesis (A and B) Coronal section of V1 shows suppression of protein synthesis in a CHX-infused hemisphere (A), but not in the noninfused hemisphere of the same animal (B), as measured by incorporation of the tritium-labeled amino acid leucine into newly synthesized proteins. Scale bar, 1 mm. (C and D) Higher-magnification inserts show markedly lower densities of silver grains in the region outlined in (A) than in (B), respectively. Scale bar, 100 μm. (E) Nissl-stained coronal section showing cortical laminae in a section adjacent to that shown in (A). Pale spots are artifacts of the Nissl staining. (F) Quantification of silver grain density over the lateral extent of CHX-infused sections (closed symbols; mean ± SEM; n = 3 animals). Solid line and gray area represent the mean and ± SEM of silver grains for the noninfused hemisphere sections. Dashed line represents background counting. Protein synthesis levels are significantly suppressed in the infused hemisphere relative to the noninfused one (∗p < 0.01, ∗∗p < 0.001, post hoc Bonferroni test). Neuron 2005 48, 329-343DOI: (10.1016/j.neuron.2005.09.016) Copyright © 2005 Elsevier Inc. Terms and Conditions

Figure 8 Loss, but Not Recovery, of Deprived Eye Response Requires Cortical Protein Synthesis (A and B) Ocular dominance histograms of animals treated with continuous intracortical infusion of CHX (10 mg/ml) in the left V1. Right eye deprivation (3 to 4 days, n = 5) during treatment induced loss of deprived eye responses in neurons located far ([A], ∼5 mm, 76 cells), but not close to ([B], up to 2 mm, 103 cells) the infusion site. (C) In contrast, restoration of binocular vision during CHX treatment (10 mg/ml) for 4 hr (140 cells, n = 4) or 3 to 4 days (139 cells, n = 5) did not prevent recovery of deprived eye responses for neurons located close to the infusion site (up to 2 mm). Animals allowed 4 hr of binocular vision were MD for 6 days and surgically implanted with minipumps 3 to 4 days before eye opening, whereas animals allowed 3 to 4 days of binocular vision were surgically implanted with minipumps 1 day before eye opening. (D) Simultaneous treatment with CHX (10 mg/ml) and RAPA (2 μM or 2 mM) did not prevent recovery of deprived eye responses close to the infusion site (up to 2 mm, 114 cells, n = 4). (E and F) In contrast, intracortical infusion of CHX (10 mg/ml) in the right visual cortex prevented recovery of deprived eye responses in neurons located close to ([F], up to 2 mm, 101 cells, n = 4), but not far from ([E], ∼5 mm, 88 cells) the infusion site. (G and H) Intracortical infusion of TTX (5 μM) in the left V1 (H) prevented recovery of previously deprived eye responses (76 cells), whereas citrate buffer infused into the right hemisphere (90 cells) of the same animals (n = 4) did not prevent recovery (G). Animals were monocularly deprived for 6 days, surgically implanted with minipumps 1 day before opening of the deprived eye, allowed 3 to 4 days of binocular vision, and then binocularly deprived for 1 to 2 days to allow elimination of TTX before recordings were conducted. Error bars indicate ±SEM. PI, pump implantation; BR, binocular recovery; BD, binocular deprivation; Cont, contralateral; ipsi, ipsilateral; RE, right eye; LE, left eye. Neuron 2005 48, 329-343DOI: (10.1016/j.neuron.2005.09.016) Copyright © 2005 Elsevier Inc. Terms and Conditions